challenge_19.py

import binascii
from Crypto.Cipher import AES
import os

plaintexts = [
"SSBoYXZlIG1ldCB0aGVtIGF0IGNsb3NlIG9mIGRheQ==",
"Q29taW5nIHdpdGggdml2aWQgZmFjZXM=",
"RnJvbSBjb3VudGVyIG9yIGRlc2sgYW1vbmcgZ3JleQ==",
"RWlnaHRlZW50aC1jZW50dXJ5IGhvdXNlcy4=",
"SSBoYXZlIHBhc3NlZCB3aXRoIGEgbm9kIG9mIHRoZSBoZWFk",
"T3IgcG9saXRlIG1lYW5pbmdsZXNzIHdvcmRzLA==",
"T3IgaGF2ZSBsaW5nZXJlZCBhd2hpbGUgYW5kIHNhaWQ=",
"UG9saXRlIG1lYW5pbmdsZXNzIHdvcmRzLA==",
"QW5kIHRob3VnaHQgYmVmb3JlIEkgaGFkIGRvbmU=",
"T2YgYSBtb2NraW5nIHRhbGUgb3IgYSBnaWJl",
"VG8gcGxlYXNlIGEgY29tcGFuaW9u",
"QXJvdW5kIHRoZSBmaXJlIGF0IHRoZSBjbHViLA==",
"QmVpbmcgY2VydGFpbiB0aGF0IHRoZXkgYW5kIEk=",
"QnV0IGxpdmVkIHdoZXJlIG1vdGxleSBpcyB3b3JuOg==",
"QWxsIGNoYW5nZWQsIGNoYW5nZWQgdXR0ZXJseTo=",
"QSB0ZXJyaWJsZSBiZWF1dHkgaXMgYm9ybi4=",
"VGhhdCB3b21hbidzIGRheXMgd2VyZSBzcGVudA==",
"SW4gaWdub3JhbnQgZ29vZCB3aWxsLA==",
"SGVyIG5pZ2h0cyBpbiBhcmd1bWVudA==",
"VW50aWwgaGVyIHZvaWNlIGdyZXcgc2hyaWxsLg==",
"V2hhdCB2b2ljZSBtb3JlIHN3ZWV0IHRoYW4gaGVycw==",
"V2hlbiB5b3VuZyBhbmQgYmVhdXRpZnVsLA==",
"U2hlIHJvZGUgdG8gaGFycmllcnM/",
"VGhpcyBtYW4gaGFkIGtlcHQgYSBzY2hvb2w=",
"QW5kIHJvZGUgb3VyIHdpbmdlZCBob3JzZS4=",
"VGhpcyBvdGhlciBoaXMgaGVscGVyIGFuZCBmcmllbmQ=",
"V2FzIGNvbWluZyBpbnRvIGhpcyBmb3JjZTs=",
"SGUgbWlnaHQgaGF2ZSB3b24gZmFtZSBpbiB0aGUgZW5kLA==",
"U28gc2Vuc2l0aXZlIGhpcyBuYXR1cmUgc2VlbWVkLA==",
"U28gZGFyaW5nIGFuZCBzd2VldCBoaXMgdGhvdWdodC4=",
"VGhpcyBvdGhlciBtYW4gSSBoYWQgZHJlYW1lZA==",
"QSBkcnVua2VuLCB2YWluLWdsb3Jpb3VzIGxvdXQu",
"SGUgaGFkIGRvbmUgbW9zdCBiaXR0ZXIgd3Jvbmc=",
"VG8gc29tZSB3aG8gYXJlIG5lYXIgbXkgaGVhcnQs",
"WWV0IEkgbnVtYmVyIGhpbSBpbiB0aGUgc29uZzs=",
"SGUsIHRvbywgaGFzIHJlc2lnbmVkIGhpcyBwYXJ0",
"SW4gdGhlIGNhc3VhbCBjb21lZHk7",
"SGUsIHRvbywgaGFzIGJlZW4gY2hhbmdlZCBpbiBoaXMgdHVybiw=",
"VHJhbnNmb3JtZWQgdXR0ZXJseTo=",
"QSB0ZXJyaWJsZSBiZWF1dHkgaXMgYm9ybi4="
]
def xor(stringToEncypt, key):

    a = bytes(a ^ b for (a, b) in zip(stringToEncypt, key))
    return a

message = "L77na/nrFsKvynd6HzOoG7GHTLXsTVu9qvY/2syLXzhPweyyMTJULu/6/kXX0KSvoOLSFQ=="
decMessage = binascii.a2b_base64(message)

# randomKey = os.urandom(16)
randomKey = os.urandom(16)
obj = AES.new(randomKey,AES.MODE_ECB)
# AES.new()

x = 0

ciphertexts = []

def ctrMode(text):
    l = len(text)//16 + 1
    nonce = x.to_bytes(length=(64 + (x).bit_length()) // 8, byteorder='little', signed=False)
    c = b""
    for i in range(l+1):
        arg = nonce + i.to_bytes(length=8, byteorder='little')
        c += obj.encrypt(arg)
    return (xor(text,c))

print(decMessage)
def encryptPlaintext():

    for plain in plaintexts:
        ciphertexts.append(ctrMode(binascii.a2b_base64(plain)))

# ctrMode(decMessage)
encryptPlaintext()
print(ciphertexts)